This invention relates to ink jet printheads, and more particularly to monolithic ink jet printheads.
Ink jet printheads create a jet of ink drops by forcing ink, under pressure, through a nozzle. Typical transducers used to pressure the ink include piezoelectric elements (i.e., acoustic ink jet) and heating resistors (i.e., thermal or bubble ink jet). An ink jet printhead usually contains an array of nozzles.
To build printheads, one approach has been to fabricate the nozzles on a separate flat plate, then attach the nozzle plate to a body containing the transducers and channels for the ink. Although this approach generally has proven adequate, it is prone to misalignment between the nozzle plate and body. Moreover, the adhesive used to join the separate parts may clog the nozzles or the channels.
To overcome the disadvantages of constructing the nozzle plate separately, some prior art printheads are constructed with the nozzle plate integral with the body. For example, U.S. Pat. No. 4,394,670, issued to Sugitani et al. on Jul. 19, 1983, U.S. Pat. No. 4,558,333 issued to Sugitani et al. on Dec. 10, 1985, and U.S. Pat. No. 4,701,766 issued to Sugitani et al. on Oct. 20, 1987 all disclose methods for fabricating monolithic printheads using hardened photosensitive resins. U.S. Pat. No. 4,438,191, issued to Cloutier et al. on Mar. 20, 1984, discloses a method of making a monolithic bubble ink jet printhead involving attaching a foundation of conductive material to a substrate, which contains heating resistors, and defining a perimeter/wall combination over the foundation and surrounding the resistors using a resist layer. After electroplating the perimeter/wall combination in place, a flash coat of metal is applied over the resist that is inside the perimeter of the perimeter/wall combination. The desired orifices and the external shape of the part are defined by a second layer of resist. The flash coat is then electroplated with a second layer of metal. Finally, the flash coat and resist layers are removed, leaving a firing chamber defined by the second layer of metal and the perimeter/wall combination, and leaving an orifice within the second layer of metal.